What are IMAP and POP?

IMAP, also known as IMAP4, and POP, also known as POP3, are two Internet mail protocols which enable you to retrieve mail from an e-mail client. For example, from your local pc you may use Netscape Messenger or Microsoft Outlook to read your e-mail. IMAP stands for Internet Message Access Protocol; POP stands for Post Office Protocol.

The IMAP protocol allows you to read your mail while it is still on the mail server. This allows you to keep your mail in a central location accessible from any IMAP-configured computer.

POP is different in that it downloads your mail to the PC, removing it entirely from the server. This is handy in that you can always read your downloaded mail on the PC, even if the network goes down. However, you won't be able to read your existing mail if you're at a different computer.

The table below summarizes some of the differences between IMAP and POP in order to help you choose which protocol is best for you.

Differences Between IMAP and POP

Question IMAP POP What does it stand for? Internet Message Access Protocol Post Office Protocol Are messages kept on the server? YES NO (by default) Will my e-mail be backed up? YES. NO. By default, all messages are downloaded to your computer and deleted from the server. The best we can do with POP is to take a "snapshot" of what is on the server at a particular instance. Can I access my mail from anywhere? YES. Since IMAP keeps all mail in a central location (the server), you can set up IMAP on multiple computers and always be able to see all your messages. NO. POP automatically downloads mail to the local computer, so if you try to set up POP on another computer, you won't be able to see old messages, and newer mail will be out of synch. How fast is it? Faster: IMAP retrieves only the message headers when you check your mail; it doesn't retrieve the entire message until you actually read it. Slower: POP downloads every message in its entirety to your computer, which can take longer with large messages. Can I filter my e-mail? YES: IMAP allows the flexibility to store messages in unique folders. NO: POP messages reside locally and you are limited in your options. You will need to create message filters on your local machine. This protocol is suitable for... ... users who want access to all their mail from multiple computers or locations. ... users who access their mail from only one location.